The present invention relates to a group III nitride semiconductor manufacturing system and more particularly to a group III nitride semiconductor manufacturing system based on a fluxing method using an alkali metal.
There has conventionally been known a group III nitride semiconductor crystal growing method based on an Na (sodium) fluxing method. This method is a crystal growth of GaN (Gallium Nitride) on a surface of a seed crystal. The process is reaction under several tenth of atmospheric pressure between nitrogen and melted Na and Ga kept around 800° C.
In the crystal growing method based on the Na fluxing method, in order to increase crystal uniformity and crystal growth stability, such an approach as rotating a crucible or rotating a seed crystal is adopted (refer to JP-A-2005-187317 and JP-A-2007-254161). In order to realize the rotation of the crucible or seed crystal, a rotational shaft is provided on the manufacturing system which holds the crucible or the seed crystal.
In this method, however, there are problems caused by the fact that Na evaporated during crystal growth enters a gap between the reaction vessel and the rotational shaft. The first example problem is interruption of rotation of the rotational shaft liquefied or solidified Na. Another one is the rotational shaft cannot be moved up and down vertically. This deficiency makes it difficult for the crucible or crystal to be taken out of the reaction vessel. In particular, in the case of Na being solidified, the rotational shaft has to be heated to melt the solidified Na.